A square grid is a grid formed by tiling the plane regularly with squares.
The grid points of a square grid of spacing 
form the point lattice 
. Kittipassorn et al. (2026) constructed a
covering of this point set by closed unit disks with
disjoint interiors for 
.
If 
is the smallest spacing admitting
such a covering, they proved
 |
Coverability is not monotone in 
, so this minimum is not a threshold
above which every spacing works. The disks cover the grid points,
rather than the entire plane.
